Phenology and Yield Losses Caused by Croton hirtus (Euphorbiaceae) in Maize (Zea mays) in Central Western Côte d’Ivoire

Croton hirtus L’Hér. (Euphorbiaceae) is a major weed in food crops in Central Western Côte d’Ivoire. However, its phenology and precise impact on crop yield are not yet known. In order to study its phenology and impact on maize crop losses, field experiments were carried out in Daloa, Central Western Côte d’Ivoire, in 2023 and 2024 for phenology study and 2023 for maize yield assessment. Croton hirtus phenology was determined according to weeding practices on five plots of 50 m2 each study year, and a phenogram was established. Yield was measured on maize plants planted along with different densities (0, 6, 12, 18, and 31 plants of C. hirtus m-2). Yield trial was laid in a randomized complete block design with three replicates per density. A linear model was performed to estimate the effect of C hirtus density on maize yield and yield loss. In terms of phenology, Croton hirtus seedlings emergence was important at the start of the growing season. Regarding weed control methods, hoeing resulted in strong emergence of seedlings of the studied weed. The application of crop-selective herbicides delayed weed emergence by one week compared to hoeing. Regarding yield, the highest maize seed yield was obtained in weed-free plots (3.84 t ha⁻¹), while maize yield at weed infestation levels of 6, 12, 18, and 31 plants m-² was reduced by 19.76%, 25.11%, 27.21%, and 32.48%, respectively, compared to weed-free plots. In light of these findings, to reduce maize yield losses to non-significant levels, it is proposed to reduce C. hirtus densities below 12 plants per m² in maize fields at the beginning of the growing season by using selective pre-emergence or post-emergence herbicides.